Nucleated cements and related methods

ABSTRACT

Methods and a kit. A cement forming method includes nucleating an acidic metallophosphate reaction mixture with first particles, resulting in forming a settable metallophosphate cement from the acidic metallophosphate reaction mixture. The first particles include a first metal oxide. Each particle of the first particles independently have a particle size in a range from about 15 microns to about 450 microns. A method for applying cement includes seeding a solution with particles, resulting in forming a settable cement from the solution. The particles have a size in a range from about 15 microns to about 450 microns. The solution includes a first metal oxide reacting with phosphate. The settable cement is applied to a substrate. A cement application kit is also described.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 13/050,013, filed Mar. 17, 2011, and entitled “Nucleated Cements andRelated Methods.”

FIELD OF TECHNOLOGY

The invention generally relates to cements and method for making andusing cements, and specifically to metallophosphate cements and methodsfor making and using the same.

BACKGROUND

Metallophosphate cements are used in many applications. For example,magnesium phosphate cements have been used as patching materials forroads. In addition, cements such as calcium phosphate and zinc phosphatecements are also used in dental applications, such as in crowns forteeth. However, the reactions are highly exothermic and proceed at veryrapid rates, making usage over large areas problematic. In addition, thehigh temperatures associated with the reactions are not compatible foruse with temperature sensitive systems. There exists a need forcontrolled methods for making and using metallophosphate cements thatare compatible with live tissue.

SUMMARY

The present invention relates to a cement forming method, comprising:nucleating an acidic metallophosphate reaction mixture with firstparticles, said first particles comprising a first metal oxide, eachparticle of said first particles independently having a particle size ina range from about 15 microns to about 450 microns, resulting in forminga settable metallophosphate cement from said acidic metallophosphatereaction mixture.

The present invention relates to a method for applying cement,comprising:

seeding a solution with particles, said particles having a size in arange from about 15 microns to about 450 microns, said solutioncomprising a first metal oxide reacting with phosphate, resulting informing a settable cement from said solution; and

applying said settable cement to a substrate.

The present invention relates to a cement application kit, comprising:

a container having at least two compartments, a first compartment ofsaid at least two compartments separated from a second compartment ofsaid at least two compartments by an openable barrier;

a first metal oxide having a particle size in a range from about 15microns to about 450 microns, said first metal oxide disposed in saidfirst compartment; and

a phosphate solution disposed in said second compartment.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the invention are set forth in the appended claims. Theinvention itself, however, will be best understood by reference to thefollowing detailed description of illustrative embodiments when read inconjunction with the accompanying drawings.

FIG. 1 is a flow chart illustrating an example of an embodiment of amethod for forming cement, in accordance with embodiments of the presentinvention.

FIG. 2A is a flow chart representing an embodiment of methods describedfor FIG. 1, in accordance with embodiments of the present invention.

FIG. 2B is a flow chart representing an embodiment of methods describedfor FIG. 1, in accordance with embodiments of the present invention.

FIG. 3 is an illustration of an embodiment of a container, in accordancewith embodiments of the present invention.

DETAILED DESCRIPTION

Although certain embodiments of the present invention will be shown anddescribed in detail, it should be understood that various changes andmodifications may be made without departing from the scope of theappended claims. The scope of the present invention will in no way belimited to the number of constituting components, the materials thereof,the shapes thereof, the relative arrangement thereof, etc., and aredisclosed simply as examples of embodiments. The features and advantagesof the present invention are illustrated in detail in the accompanyingdrawings, wherein like reference numerals refer to like elementsthroughout the drawings. Although the drawings are intended toillustrate the present invention, the drawings are not necessarily drawnto scale.

FIG. 1 is a flow chart illustrating an example of an embodiment of amethod for forming cement. Step 100 comprises forming a metallophosphatereaction mixture. The metallophosphate reaction mixture may, forexample, be formed by combining a first metal oxide 115 with a phosphatesource 110, such as by combining the first metal oxide 115 with asolution of phosphate. The combining of the first metal oxide 115 andthe phosphate source 110 may result in a reaction between the firstmetal oxide 115 and the phosphate source 110 in solution. For example,dissolving a first metal oxide into a solution containing phosphate, mayresult in the phosphate reacting with the first metal oxide. Thephosphate source may comprise a solid or a liquid. The phosphate sourcemay comprise, for example, an aqueous solution of a phosphate compound.Examples of suitable phosphate compounds include monopotassiumphosphate, dipotassium phosphate, tetrapotassium pyrophosphate,potassium tripolyphosphate, orthophosphoric acid, orthophosphate,polyphosphoric acids, polyphosphates, branched polyphosphates, phosphateesters, phosphite esters, branched polyphosphates, cyclophosphoricacids, metaphosphoric acids, cyclophosphates, metaphosphates, phosphoricanhydride, the like, and combinations thereof.

Examples of suitable metal oxides include magnesium oxides, aluminumoxides, zinc oxides, iron oxides, barium oxides, calcium oxides, yttriumoxides, cerium oxides, titanium oxides, zirconium oxides, siliconoxides, and combinations thereof. In embodiments using MgO as a metaloxide may comprise light burned MgO, dead burned MgO, hard burned MgO,or a combination of these.

The first metal oxide 115 may comprise particles of the first metaloxide 115 having a particle size. The particles may each independentlyhave a particle size in a range from about 15 microns to about 40microns. The concentration of the phosphate in the solution may be instoichiometric excess with respect to the concentration of the firstmetal oxide 115 in the solution, i.e. the phosphate may be in excess ofthe first metal oxide. Reacting the first metal oxide 115 withphosphoric acid may result in forming an acidic metallophosphatereaction mixture, which may be in the form of a fluid such as solutionor slurry. The pH of the acidic metallophosphate reaction mixture may beless than about 6, such as between about 3 and about 5.

After forming the acidic metallophosphate reaction mixture, the reactionmixture may be cooled, such as to ambient temperatures (such as betweenabout 20° C. and about 40° C.) or sub-ambient temperatures, such asbelow about 20° C. The reaction between the metal oxide and thephosphate may be exothermic, and thus cooling the reaction mixture mayserve to bring the temperature of the reaction mixture to a moremanageable temperature for handing and/or for biologically relatedusage, and/or may drive the reaction equilibrium farther to completion.

Step 105 comprises nucleating the metallophosphate reaction mixture ofstep 100, resulting in forming a settable metallophosphate cement fromthe acidic metallophosphate reaction mixture. As used herein, the termsettable means having the ability to set, cure, harden, fix, stiffen, orotherwise transform from a fluid consistency to a solid consistency,through chemical reaction, physical transformation, or a combinationthereof. Nucleating may comprise, for example, seeding the reactionmixture of step 100 by adding particles to the reaction mixture,resulting in the particles forming nucleation centers or sites ofcrystal or aggregate formation of a metallophosphate cement. Forexample, nucleating may comprise seeding a solution with particles,where the solution comprises a first metal oxide reacting withphosphate.

The particles for seeding may comprise any material on which ametallophosphate cement may aggregate or crystallize. Examples ofsuitable materials for particles for seeding include ceramic, a secondmetal oxide, metals such as silver, metallophosphate compounds,materials coated with one or more metallophosphate compounds,crystalline compounds such as those having Mg or K in their chemicalstructure, or combinations thereof. Other examples of suitable materialsinclude materials having EMF-(electromagnetic field) or photon-activatedsurfaces. In some embodiments, the particles for seeding may compriseparticles of crushed ceramic or cement such as hardened metallophosphatecement. In another embodiment, the particles may comprise silicaparticles coated with metallophosphate cement.

The particles for seeding may each independently have a particle size ina range from about 15 microns to about 450 microns. For example, afterforming a solution comprising phosphoric acid reacting with a metaloxide, the solution may be seeded with particles of a second metal oxidehaving sizes in a range from 15 microns to about 450 microns, resultingin forming a settable cement from said solution. The particles forseeding may comprise nanoparticles and may have a particle size in arange from about 0.33 nanometers (nm) to about 1000 nm. The relativelylarge surface area of nanoparticles may allow for increased reactionrates.

The particles for seeding may, for example, comprise a second metaloxide. The second metal oxide may be the same or different from thefirst metal oxide 115 used to form the metallophosphate reaction mixtureformed in step 100. Examples of suitable oxides for the second metaloxide include those listed above. The second metal oxide may compriseparticles of the second metal oxide, where each particle of the firstparticles independently have a particle size in a range from about 15microns to about 450 microns. In another embodiment, each particle ofthe first particles may independently have a particle size in a rangefrom about 0.33 nm to about 1000 nm. The second metal oxide may reactwith a portion of the phosphate in the metallophosphate reactionmixture. The particles of the second metal oxide may form nucleationsites within the mixture, resulting in forming a settablemetallophosphate cement. The amount of the second metal oxide added maybe such that the sum of the molar amount of the first metal oxide 115and the molar amount of the second metal oxide is a stoichiometricamount of metal oxide with respect to the phosphate. In embodimentswhere the amount of the first metal oxide is less than a stoichiometricamount with respect to the phosphate in solution, the molar sum of theamounts of the second metal oxide and the first metal oxide may be in arange from a stoichiometric amount to about 50% excess of astoichiometric amount, with respect to the phosphate. The reaction ofthe second metal oxide with the phosphate in the metallophosphatereaction mixture may raise the pH to greater than about 6.

Blending the second metal oxide with the composition may comprise addingparticles of the second metal oxide to the composition until the pH ofthe resulting mixture is greater than about 6. The second metal oxidemay be added continuously or in intermittent small quantities. In someembodiments, the second metal oxide may be automatically added until thepH is greater than about 6. For example, an automated mixing system maymeasure the pH of the mixture as the second metal oxide is added,stopping the addition of the second metal oxide when the pH reaches apredetermined value, such as a value greater than about 6.

A third material or additive may be mixed with the metallophosphatereaction mixture, such as a filler or a reinforcing material, forexample. The reaction mixture may comprise up to about 30% by weight ofthe third material. Examples of the third material include silica,wollastonite, silica fume, coesite, flyash, fiberglass, carbon fiber,basalt fiber, polymers, biological materials, nanoparticles, spidersilk, Superconducting Quantum Interference Devices (SQUIDs), plantmaterials, and combinations thereof. An example of plant material isrice husk.

The third material may include a gas such as air, argon, nitrogen,oxygen, the like, and combinations thereof. For example, the inclusionof air gaps in the final set cement may increase biocompatibility. Thethird material may comprise a reactive gas such as chlorine or fluorine.

The third material may be selected to adjust the final properties of thecured cement, where such properties may include density, thermalexpansion, hardness, magnetism, conductivity, combinations thereof, etc.For example the third material may comprise a polymer such aspolystyrene, such as polystyrene foam for example. The use ofpolystyrene foam may reduce the density of the cement. Other materials,such as carbon fiber, may be used as a third material to increase thestrength and/or heat resistance of the cement. The use of magneticmaterials, such as iron, may be used to render the cement magnetic. Theuse of fly ash may increase the workability or flowability of thecement. The third material may be mixed before or during the blending ofthe second metal oxide with the metallophosphate reaction mixture formedin step 100 above.

The third material may comprise a reactive filler, where a reactivefiller is described as a filler which raises the pH of themetallophosphate reaction mixture. Fly ash and fibrous wollastonite, andpowdered wollastonite are examples of reactive fillers. In embodimentswhere a reactive filler is added, the amount of oxides and/or phosphatemay be adjusted to produce a final pH in a suitable range for a settablecement, such as greater than about 6. The methods described herein arenot limited to any particular filler, and those skilled in the art willrecognize there exist numerous suitable fillers, all of which areintended to be included within the scope of embodiments disclosedherein.

Step 130 comprises applying the settable cement to a substrate. Thesubstrate may comprise a material such as cement, concrete, stone,glass, animal bone, animal tooth material, animal tissue, wood, metal,plastic, ceramic, crystalline material, plant material (such as burlap)and combinations thereof. For example, the settable cement may be usedto reconstruct a section of bone in a patient (such as in a fracturedarea), where the cement is applied to the portion of bone, either in asingle application or in multiple applications, and allowed to set orharden, resulting in forming a repaired and/or reinforced area along thesection. In another example, the surface may comprise concrete, wherethe settable cement may be applied to fill or otherwise repair a crackor opening in a section of concrete. The settable cement may be used tofill the section and then allowed to harden, resulting repairing thebroken section of concrete.

The cements and related methods described herein may be at ambient orsub-ambient temperatures during curing and thus have an advantage overcompositions requiring thermal curing. Settable cement compositionsrequiring thermal curing at elevated temperatures may not be suitablefor use in temperature sensitive applications. The ambient andsub-ambient temperatures of the curing steps described herein arecompatable with temperature sensitive systems, such as live tissue, andare practical for use in areas where thermal curing is not possible,such as concrete repair. The ambient and sub-ambient temperatures of thecements described herein may also permit the safe embedding oftemperature sensitive elements, such as electronics and plastics. Inaddition, the use of ambient and sub-ambient temperatures for themethods described herein may allow for the use of temperature sensitiveadditives which may impart improved properties on the final set cement.For example, the use of biomaterials may be incorporated into thereaction mixtures described herein without thermal degradationassociated with high temperature curing methods, by the use of ambientor sub-ambient curing conditions.

The cements described herein may be amorphous, crystalline, orsemi-crystalline in structure. Crystalline and semi-crystallineembodiments of the cements herein may be similar in structure toceramics, yet do not require the thermal curing which is characteristicof ceramics. Thus the cements described herein may be described ascomprising a hybrid between cement which cures by reaction with water atambient temperature and ceramic having crystalline or semi-crystallinestructure.

FIG. 2A is a flow chart representing an embodiment of methods describedfor FIG. 1 above. A phosphate source 200 (such as a phosphoric acidsolution) is combined with a first metal oxide 205, such as MgO,resulting in forming a reaction mixture in step 210. The phosphate 200may be in stoichiometric excess with respect to the metal oxide 205,resulting in an reaction mixture having a pH lower than about 6, such asbetween about 3 and about 6.

A non-reactive filler may be added in step 215 to the reaction mixture.A non-reactive filler is described as a filler which does not affect thepH of the reaction mixture, such as silica or carbon fiber. A reactivefiller may be added in step 220, where a reactive filler is described asa filler which affects the pH of the reaction mixture, such as fly ashwhich may increase the pH.

Step 225 comprises seeding or nucleating the reaction mixture withparticles of a second metal oxide. The addition of the second metaloxide may raise the pH of the reaction mixture above about 6, resultingin the formation of a settable metallophosphate cement in step 230. Anexample reaction is shown below:

5H₂O+KH₂PO₄+MgO→MgKPO₄.6H₂O

where a first metal oxide comprising MgO reacts with a phosphate sourcecomprising KH₂PO₄ resulting in forming a metallophosphate cementMgKPO₄.6H₂O.

The second metal oxide may comprise a metal oxide as described above,and may have particle sizes in a range from about 15 microns to about450 microns. In another embodiment, the particle sizes may be in a rangefrom about 0.33 nm to about 1000 nm. The particles of the second metaloxide may act as nucleation sites for the crystallization ofmetallophosphate compounds resulting from the reaction of the phosphatewith the first metal oxide, a portion of the second metal oxide, orboth. The first and second metal oxides may be the same or different.

The amount of the second metal oxide added may be determined by the pHof the reaction mixture. For example, as amounts of the second metaloxide are added to the reaction mixture, the pH of the reaction mixturewill rise. The addition of the second metal oxide may be stopped whenthe pH reaches a predetermined value, such as above about 6. The secondmetal oxide may be added until the combined molar amount of the firstmetal oxide and the second metal oxide are between about astoichiometric amount and about 50% in excess of a stoichiometric amountwith respect to phosphate, such as between about 10% and about 50% inexcess of a stoichiometric amount.

The rate of reaction may be slowed by the use of fillers, which maybehave as a heat sink to cool the reaction between the phosphate and themetal oxides. The rate of reaction may be slowed by the use of deadburned MgO as a metal oxide as compared with other forms of magnesiumoxide. The rate of the reaction may be slowed by cooling the reactionmixture. The rate of the reaction may be slowed by the addition of acid,thus lowering the pH, as desired by a user.

In some embodiments, the addition of the reactive and non-reactivefillers may be performed after the addition of the second metal oxide.The example shown in FIG. 2A is not meant to be limited by the order ofthe steps, rather to show an example of an embodiment.

FIG. 2B is a flow chart representing an embodiment of methods describedfor FIG. 1 above. A phosphate source 200 (such as the phosphate sourcesdescribed above) is combined with a first metal oxide 205, such as themetal oxides described above, resulting in forming a reaction mixture instep 240.

A filler may be added in step 245, such as the reactive and non-reactivefillers described above. The filler may be added immediately followingstep 240, or at a later point in the method, and is not necessarilylimited to the order shown in FIG. 2B.

Step 250 comprises seeding or nucleating the reaction mixture withparticles, where the particles may comprise any material on which ametallophosphate cement may aggregate or crystallize, such as theparticles for seeding described above.

After nucleating in step 250, acid 255 may be added to the reaction tolower the pH. Lowering the pH may slow the reaction, resulting inallowing additional working time or for the addition of otheringredients, such as other fillers or additional metal oxides forexample.

Step 260 comprises adding additional materials to the reaction. Suchmaterials may comprise fillers or one or more metal oxides, for example.The metal oxides may not necessarily be added in a single step, ratherstep 260 may comprise a plurality of additions of smaller amounts ofmetal oxide. Step-wise addition of metal oxide in step 260 may allow forincreased control of the reaction rate.

In some embodiments, the methods described above may utilize a cementapplication kit. The kit may comprise a container having at least twocompartments, such as a first compartment and a second compartment. Eachcompartment of the at least two compartments may be separated fromadjacent compartments by one or more openable barriers blocking orotherwise preventing the flow or transfer of material from onecompartment into an adjacent compartment.

An openable barrier may be described as a barrier which, in one state,may prevent the flow of material and which, in a second state, may beopened, broken, altered, or removed, thus allowing material to flow fromone compartment into an adjoining compartment. Examples of openablebarriers include valves, breakable or removable plugs, breakable orremovable membranes, the like, or a combination of these. In someembodiments, the openable barrier may comprise a meltable plug ormembrane (such as a wax plug or membrane), which may melt at a specifiedtemperature, thus opening to allow flow of material from one compartmentinto another. The blocking by the openable barrier may comprise blockingin one direction or both directions. For example, an openable barrierwhich blocks flow in only one direction, may comprise a one-way checkvalve.

In some embodiments, the compartments may be interconnected by channels.The channels may each have an openable barrier disposed thereinpreventing the flow of material through each channel into an adjoiningcompartment. For example, a first compartment may be connected to thesecond compartment through a first channel. In another embodiment, athird compartment may be connected to the second compartment through asecond channel, to the first compartment through a third channel, orboth.

The compartments of the container may hold and separate components usedin the cement forming methods described herein. For example, a firstmetal oxide may be disposed inside a first compartment and a phosphatesolution may be disposed in a second compartment. The phosphate solutionmay comprise phosphate compounds as described above. The first metaloxide may comprise a metal oxide as described above, such as a metaloxide having a particle size in a range from about 15 microns to about450 microns, or a metal oxide having a particle size in a range fromabout 0.33 nm to about 1000 nm.

The container may comprise a second metal oxide disposed inside a thirdcompartment, where the first and second metal oxides may be the same ordifferent. The first metal oxide may have a particle size in a rangefrom about 15 microns to about 40 microns, and the second metal oxidemay have a particle size in a range from about 15 microns to about 450microns.

A user may mix the first metal oxide in the first compartment with thephosphate solution in the second by opening an openable barrier betweenthe first and second compartments and transferring the contents of onecompartment into the other. For example, the phosphate solution may betransferred into the compartment containing the metal oxide, to form asolution comprising the first metal oxide reacting with the phosphate.Then the second metal oxide may be added to the solution, resulting informing a settable cement from the solution.

FIG. 3 is an illustration of an embodiment of a container 300 comprisingat least two compartments, as described above. The container 300 of FIG.3 comprises a first compartment 305, a second compartment 310, and athird compartment 315. The container 300 comprises openable barriers320, 321, and 322, where the openable barriers prevent the flow ofmaterial between adjacent compartments. Opening the openable barriersmay allow material disposed in one compartment to flow into an adjacentcompartment. For example, opening openable barrier 320 may allowmaterial to flow from compartment 305 into compartment 310, or fromcompartment 310 into compartment 305.

The foregoing description of the embodiments of this invention has beenpresented for purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the precise formdisclosed, and obviously, many modifications and variations arepossible. Such modifications and variations that may be apparent to aperson skilled in the art are intended to be included within the scopeof this invention as defined by the accompanying claims.

1. A method for applying cement, comprising: seeding a solution withparticles, said particles having a size in a range from about 15 micronsto about 450 microns, said solution comprising a first metal oxidereacting with phosphate, resulting in forming a settable cement fromsaid solution; and applying said settable cement to a substrate.
 2. Themethod of claim 1, wherein said solution of phosphate further comprisesa third material selected from the group consisting of silica,wollastonite, silica fume, coesite, flyash, fiberglass, carbon fiber,basalt fiber, polymers, biological materials, plant material,nanoparticles, spider silk, Superconducting Quantum InterferenceDevices, and combinations thereof.
 3. The method of claim 1, whereinsaid substrate comprises a material selected from the group consistingof cement, concrete, glass, stone, animal bone, animal tooth material,animal tissue, metal, plant material, plastic, wood, ceramic,crystalline material, and combinations thereof.
 4. The method of claim1, wherein said particles comprise a material selected from ceramic, asecond metal oxide, metallophosphate compounds, materials coated withone or more metallophosphate compounds, crystalline compounds having Mgor K in their chemical structure, and combinations thereof.
 5. Themethod of claim 1, wherein said particles comprise a second metal oxide,said first metal oxide and said second metal oxide each independentlyselected from the group consisting of magnesium oxides, aluminum oxides,zinc oxides, iron oxides, barium oxides, calcium oxides, yttrium oxides,cerium oxides, titanium oxides, zirconium oxides, silicon oxides, andcombinations thereof.
 6. The method of claim 1, wherein said solution ofphosphate comprises an aqueous solution of a phosphate compound, saidphosphate compound selected from the group consisting of monopotassiumphosphate, dipotassium phosphate, tetrapotassium pyrophosphate,potassium tripolyphosphate, orthophosphoric acid, orthophosphate,polyphosphoric acids, polyphosphates, branched polyphosphates, phosphateesters, phosphite esters, branched polyphosphates, cyclophosphoricacids, metaphosphoric acids, cyclophosphates, metaphosphates, phosphoricanhydride, and combinations thereof.
 7. The method of claim 1, whereinsaid first metal oxide is in a first amount less than a stoichiometricamount with respect to said phosphate.
 8. The method of claim 1, whereinsaid particles comprise a second metal oxide, a molar sum of said firstmetal oxide and said second metal oxide in a stoichiometric ratio ofmetal oxide with respect to said phosphate.